Currently, when streaming UPnP or Google Cast (or Apple TV) a client can see and stream to all receivers. While this may be acceptable in a secure home environment with only authorized users, it might not be ideal in a business environment or an environment that may have guest users (where the technologies are increasingly being used).
As an example, an office might set up multiple stream receiving TVs (or separate boxes) in an office building including locations such as conference rooms, executive offices, etc. The current technology could enable screen hijacking or mistakes by transmitting parties. For example, an employee who attempts to stream a PowerPoint presentation to a screen in the local conference room might accidentally stream the presentation to the CEOs office; or a presentation to be viewed by the CEO may mistakenly be streamed to a public conference room.